Hum elimination



Feb. 12,1935. B. sALzBERG HUM ELIMINATION Filed Dec. 30, 1950 Rummy-'I lll IMT

NKY/HIE INVENTOR BERNARD SAL'LBERG BY ff@ @WM ATTORNEY Patented Feb. 12, 1935 UNITED STATES HUM ELIMINATION nerim-a salzberg; aooeky Point, N. Y., assigner-'t0 Radio Corporation of America, a corporation of K Delaware Application December 30, 1930, Serial No. 505.488.

This invention appertains tothe art of high frequency communication and more particularly towards the elimination of modulation due to hum in electron discharge devices.

Polarizing potentials for electron discharge devices and electron discharge device oscillators are often times derived from a source of rectied alternating current. 'I'he supply potentials, therefore, are in reality potentials having a constant component and an alternating component, or in other words, potentials that though unidirectional have an undulating component therein. The undulating component produces, in the case of oscillators, an undesired modulation of the generated oscillations which manifests itself, in the receiving end of the system, in an annoying hum.

An object of the present invention is to eliminate the foregoing defect, and to do so, in accordance with the present invention, there is connected across the source of undulating unidirectional potential, an impedance, usually in the form of a resistance, from which the desired polarizing potentials may be obtained. Connections are then made to the resistor, in a manner which will be more fully explained hereinafter, in a fashion such that the effects of the undulating component on the electron stream or streams of the device or devices, appearing in the resistor, are substantially eliminated.

Still a further object of the present invention is to apply the foregoing hum elimination scheme to a pair of electron discharge devices having like electrodes connected in series for oscillatory energy or, more particularly, to electron discharge devices connected together in pushpull.

Still a further object of the present invention is to apply the aforementioned hum elimination scheme to an ultrashort wave length oscillation 40 generator-and specifically of the type wherein electrons oscillate about the intermediate electrode or grid of an electron discharge device.

The invention is more fully described in connection with the accompanying drawing wherein Figures 1 and 2 illustrate schematically electron discharge device systems wherein the eiiects of the undulating component, appearing in an .undulating unidirectional source of polarizing potential, upon the electron streams of the devices, are substantially eliminated.

Turning to Figure 1 of the drawing, across a source of undulating unidirectional potential or rectier 2, there is connected an impedor, usually in the form of a resistor 4. Polarizing potentials 5 are applied to the grids, intermediate or control 11' claims. `(c1. 25o-21) electrodes 6, 8 of electron discharge devices 10, 12 through conductor 14 and tuned circuit 16 serially connecting the grids 6, 8 together. Tuned circuit 16 is especially adapted for ultrashort wave length energy and consists preferably of a single looped 5 conductor having U-shaped slides 18, 20 therein for varying the effective length and hence the tuning of circuit 16.

The anodes 22, 24 of electron discharge devices 10, 12 are similarly serially connected together l0 for oscillatory energy by a similar tuned circuit 26 having tuning slides 2 8, 30 therein.

The anode circuit is completed to resistor 4 through conductor 32 which-,supplies polarizing potentials to the anodes, source of potential 34 l and transformer 36 to which modulating potentials from transmitter 38 amplifled by amplifier 40 are applied,

By virtue of the high positive potential imparted to the ogrids of the electron discharge devices and the relatively low negative or positive potential applied to the plates, velectrons oscillate about the grid, producing currents of ultrashort wave length. This action is known in the art and hence need not be further described here. The modulated oscillations resulting from the application of modulating potentials to the anode circuit through the action of transformer 36, are fed through blocking condensers 42, 44 and transmission line 46 to a suitable radiating antenna 48, for radiation to a suitable receiving system (not shown).

Ordinarily, haphazard polarization of the anodes and control electrodes from a rectifier would result, as already stated hereinabove, in an undesired modulation of the instantaneous amplitude and frequency of the generated oscillations. This defect is remedied according to the present invention by suitably tapping the cathodes through conductor 50 to resistor 4 such that the indulating voltage variations appearing across the portions of resistor 4 on either side of tapping point 50 produce nullifying effects upon electron streams of electron discharge devices 10, 12; or, in other words, prevent the undulating compol nent of unidirectional source 2 from modulating the oscillations generated.

In general, the setting of the voltage divider 50, which is required to eliminate the frequency modulation due to voltage ripple, diifers from that required to eliminate the amplitude modulation (due toy the same cause). Both modulation components may be eliminated with the same balance setting by suitable construction of tubes, 0r by proper choice of oscillation frequency. 55

If frequency modulation of the oscillating current is employed for the communication of intelligence, it is merely necessary to arrange the differential balance so that the frequency modulation component due to voltage ripple is eliminated. The amplitude component'may then be eliminated by employing limiting, either at the transmitter or receiver. If amplitude modulation of the oscillating current is employed for the communication of intelligence, the differential balance should be arranged so that the amplitude modulation component due to voltage ripple is eliminated. 'I'he periodic shift in operating frequency, due to ripple in the supply voltage,

may then be taken care of by means of a broad band pass circuit at the receiving end.

When the operating frequency is of the same order as the alternating components of the voltage supply, it is desirable to allow for a phase, as well as amplitude balance. This may be accomplished by arranging the diierential balance 4, of Figure 1, or 58, of Figure 42, in the form of an impedance, usually consisting of the resistors shunted by suitably divided capacitors.

Should the tapping point 50 result in a wrong bias for the anodes of the devices, an additional source 34, preferably in the form of a battery, may be inserted in the conductor 32 as shown, which will bring the anode potential up or down as desired to the correct polarizing value.

It is not necessary that the cathodes be connected intermediate the ends of resistor 4 as shown in Figure 1, but, for suitable adjustment, as shown in Figure 2, a variable impedor, usually in the form of ah resistor 58-may be connected between the cathodes of electron discharge device oscillators 10, 12 and one end of impedor 4. By suitable adjustment of resistor 58, the component effects of the undulating component from source 2 may be rendered nil.

It is evident that the foregoing scheme, though illustrated in connection with transmitters and pushpull arranged tubes, is not limited `solely thereto; for, to one skilled in the art, the present invention as described is readily applicable to a receiving system or to an ordinary amplifying system of any range of frequencies. Consequently, the present invention is not to be limited in scope except as indicated by the appended claims.

Having thus described my invention, what I claim is:

1. In a high frequency communication system, an electron discharge device oscillator having anode, cathode and control electrodes, a source of undulating unidirectional potential for polarizing said control and anode electrodes, connections from said source to the control and anode electrodes for applying opposite potentials thereto, and a connection from said cathode electrode to a single pointon said source, said connections being adapted to substantially eliminate the effects of the undulating component of said source of potential on said electron discharge device'oscillator, another source of potential connected to said anode for aiding in polarizing same, means for modulating the oscillatory energy of said oscillator, and means 'for transmitting the modulated oscillations.

2l In a high frequency transmitting communication system, a pair of electron discharge device oscillators each having an anode, a cathode and an intermediate electrode, a source of undulating unidirectional potential, an impedance across said source, means for connecting both cathodes of said devices to a singlev point intermediate the terminals of said impedance, means for directly connecting the intermediate electrodes of said f streams of said devices. and means for serially connectingtogether like electrodes of each device with reference to oscillatory energy.

3. In 'a high frequency communication system, a pair of pushpull connected electron discharge devices each having an anode, a cathode and a grid, a high frequency circuit serially connecting the grids together, said circuit having one or more U-shaped slides therein for varying the tuning thereof, a high frequency circuit' serially connecting the anodes together, said last mentioned circuit having one or more U-shaped slides therein for varying the tuning thereof, a source of undulating unidirectional potential, a resistor connected across said source, and means for connecting opposite potentials from said source to said anodes and grids, and a connection from said cathodesto said resistor for substantially eliminating the eiects of the undulating component of said unidirectional source on the electron streams of said devices.

l 4. In a high frequency communication system, an electron discharge device having an anode, a cathode and a grid, a source of undulating unidirectional potential, an impedance connected across said source, means for connecting the anode and grid of said electron discharge device to said impedance for suitably polarizing said anode and said grid, and, a variable resistor for coupling the cathode of said device to said impedance for eliminating the effect of the undulating potential component appearing across said impedance upon the electron stream of said device.

5. In a high frequency communication system, a pair of electron discharge devices each havingv an anode electrode, a cathode electrode and a grid electrode, corresponding electrodes of said devices being connected together, a source of undulating unidirectional potential, a resistor connected across said source, connections from said resistor to said anodes and grid for suitably polarizing the same, a variable resistor, a connection from said variable resistor toV the cathodes of said devices, and a connection from said variable resistor to said first mentioned resistor for substantially eliminating the effects of the undulating component of said source upon the electron streams of said devices.

6. In a high frequency communication system, a pair of push-pull connected electron discharge devices, each having an anode, a cathode and a grid, a source of undulating unidirectional potential, a resistor across said source, and means connecting the positive potential end of said resistor to said grids and the negative potential end of said resistor to said anodes, and a connection from said cathodes to said resistor for substantially eliminating the effects of the undulating potential component of said unidirectional source on the electron streams of said devices.

7. In a high frequency communication system, a pair of push-pull connected electron discharge devices, each having an anode, a cathode and a grid, a source of undulating unidireca tional potential, a resistor across said source,

and means connecting the positive potential end of said resistor to said grids and the negative potential end of said resistor to said anodes, and a source of direct current potential intermediate said negative potential end of said resistor and said anodes, said last source being connected in opposition to the negative potential from said resistor, and a connection from said cathodes to said resistor for substantially eliminating the effects of the undulating potential component of said unidirectional source on the electron streams of said devices.

8. In a high frequency communication system, an electron discharge device having an anode, a cathode and a grid, a source of undulating unidirectional potential, an impedance connected across said source, connections from the anode and grid of said electron discharge device to said impedance for suitably polarizing said anode and said grid, the: connection from said anode to said impedance including a source of direct current potential, and a connection for coupling the cathode of said device to a point intermediate the terminals of said impedance for eliminating the eiect of the undulating potential component appearing across said impedance upon the electron stream of said device.

9. In a high frequency communication system, a pair of push-pull connected electron discharge devices each having an anode, cathode and grid, a high frequency circuit serially connecting the grids together, said circuit having means for varying the tuning thereof, a high frequency circuit serially connecting the anodes together, said last mentioned circuit having means for varying the tuning thereof, a source of lundulating unidirectional potential, a resistor connected across said source, and means for connecting opposite potentials fronrsaid source to said anodes and grids, andl a connection from said cathodes to said resistor for substantially eliminating the effects of the undulating component of said unidirectional-source on the electron streams of said devices.

10. In a high frequency communication system, an electron discharge device having an anode, a cathode, and a grid, a source of undulating unidirectional potential, an impedance connected across said source, means for supplying from said impedance a positive potential to said grid and a much lower potential to. said anode with respect to said cathode, said means including a source of potential in circuit with the anode of said device, said cathode being coupled to said impedance for eliminating the eect of the undulating potential component appearing across said impedance upon the electron stream of said device.

11. In a high frequency communication system, an electron discharge device having an anode, a cathode, and a grid, a source of undulating unidirectional'potential, an impedance connected across said source, means for supplying from said impedance a positive potential to said grid and a much lower potential to said anode with respect to said cathode, said cathode being coupled to said impedance for eliminating the effect of the undulating'potential component appearing across said impedance upon the electron stream of said device.

BERNARD SALZBERG. 

